/*
 * Copyright (c) Kumo Inc. and affiliates.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <string>

#include <boost/regex/pending/unicode_iterator.hpp>

#include <melon/range.h>

namespace melon {
    class UTF8StringPiece {
    public:
        using iterator = boost::u8_to_u32_iterator<const char *>;
        using size_type = std::size_t;

        /* implicit */
        UTF8StringPiece(const melon::StringPiece piece)
            : begin_{piece.begin(), piece.begin(), piece.end()},
              end_{piece.end(), piece.begin(), piece.end()} {
        }

        template<
            typename T,
            std::enable_if_t<std::is_convertible_v<T, melon::StringPiece>, int>  = 0>
        /* implicit */ UTF8StringPiece(const T &t)
            : UTF8StringPiece(melon::StringPiece(t)) {
        }

        iterator begin() const noexcept { return begin_; }
        iterator cbegin() const noexcept { return begin_; }
        iterator end() const noexcept { return end_; }
        iterator cend() const noexcept { return end_; }

        bool empty() const noexcept { return begin_ == end_; }

        size_type walk_size() const {
            return static_cast<size_type>(std::distance(begin_, end_));
        }

    private:
        iterator begin_;
        iterator end_;
    };
} // namespace melon
